Luffy: Brutalize the Straw Hats, treat your own comrades like trash, attack the straw hat, ruin the mystery of One Piece, or talk shit about meat.
Zoro: Tell him that Kuina killed herself, show him Sanji's new wanted poster, or make fun of his sense of direction.
Nami: Treat children like shit, burn her trees, or go "SHAHAHAHAHA" near her.
Usopp: Call him dead weight or bring up his mom and Yasopp.
Sanji: Throw away food, hit a girl (not guaranteed, depends on situation), or say Zoro is stronger.
Chopper: Call him a monster and treat him like he isn't a person, or bring up his bounty poster.
Robin: Destroy ruins, burn books, or say/insinuate that Ohara deserved the buster call.
Franky: Brutalize the Franky Family, steal his trunks, be a Cipher Pol agent, or bring up the 94 million bounty poster. Not taking responsibility for your own creations would probably piss him off too.
Brook: Attack his afro or say something like "That whale at the Twin Capes sure was tasty!"